Stairs constitute a permanent problem specifically for wheelchair drivers and people with impaired mobility. A stair-climbing device as mentioned above, for example, provides the possibility that an assisting person can transport a wheelchair driver or a person with impaired mobility upstairs or downstairs without particular physical effort merely with the assistance of such stair-climbing device. In order to achieve this, such stair-climbing device can be detachably mounted to a wheelchair, provided that the support unit is not designed as a part of the wheelchair as such. Together with the wheelchair, the stair-climbing device is driven to the first step of a flight of stairs. An assisting person tilts the stair-climbing device together with the attached wheelchair towards his or her direction in a position of balance. When the ideal tilting position is reached, the assisting person only feels a minimum force in a forward or rear direction. Upon operation of the climbing unit of the stair-climbing device, a climbing element now gets in contact with the upper surface of the next step and lifts the stair-climbing device on the next step. This operation is repeated until the stair-climbing device has reached the topmost step of the stair. Climbing down is there effected in an analog way in the same manner.
Conventional stair-climbing devices have the disadvantage that the climbing operation is effected in a jerky manner. An operator therefore during the climbing operation has to balance load change reactions which due to the fact that they occur quickly, that means within a short period of time, are clearly sensible.
The stair-climbing device according to DE 199 12 932 C1 deals with this problem such that the climbing unit can be operated with varying propulsion speeds, wherein the propulsion speed shortly before contact of a climbing element on the surface of the next step is reduced as compared with a predetermined propulsion speed so that a soft touchdown is achieved and after the touchdown on the next step the propulsion speed is increased again to the first predetermined propulsion speed.
However, even in case of this concerning its safety features considerably improved stair-climbing device operation errors cannot be excluded. An operation error could be that the climbing operation is started by an operator when the stair-climbing device is in a position which is not suitable. Such unsuitable position for instance could be if the stair-climbing device is too remote from the next step or is skewed with respect to a next step in a too large angle.
DE 297 21 477 U1 discloses a stair-climbing device which is designed such that it always rests on two steps, namely either on two adjacent steps or, in case of narrow and wound stairs, on one and the second next step. This is intended to unburden the operating person as far as physical efforts are concerned so that only guiding and steering operations are to be performed.
In case of this known stair-climbing device, on the left hand side and right hand side of the rear side touch sensors in the form of contact strips are attached which are operated upon contact with the next higher edge of a step and thereby activate the driving source for the next climbing operation.
Furthermore, touch sensors can be attached at the climbing elements which ensure that each climbing step starts from a defined position of the climbing structure and ends at a defined position.
The climbing operation of this known stair-climbing device occurs practically without tilting movements according to operation. Furthermore, it comprises climbing means which do not allow displacement on the step of a stair during operation. These climbing means, however, are very complex. Furthermore, such climbing systems which are continuously in engagement with a plurality of steps so that a crawler-like climbing operation is effected raise problems concerning specific geometries of stairs, specifically spiral staircases and furthermore have large structural dimensions.